Effects of Loading Frequencies on Fatigue Strength of Aluminum 6061-T6

Abstract

Abstract Material fatigue properties include a fatigue strength at a given number of cyclic stresses and fatigue life at a specified cyclic stress level. Typically, provided material fatigue properties don’t show or specify whether there is any effect of cyclic loading frequency on fatigue strength. Some research concluded that the effects of cyclic loading frequency on fatigue strength are very limited and can be ignored. But some research indicated that there are significant effects of cyclic loading frequency on fatigue strength and cannot be ignored. Lots of literature evaluates the effects of ultrasonic load frequencies on material fatigue strength. But most of the component failures in industries are due to the not-ultrasonic cyclic stresses which are typically induced by rotating unbalance or mechanical vibration. When evaluating the effects of load frequencies on material fatigue strength, a lot of literature compared the S-N curves. But metal fatigue is the initiation and propagation of inherent defects or cracks in a component due to cyclic loading. Because inherent defects or cracks are randomly distributed and randomly initiated ins a component, fatigue failure is a random event. This paper studies the effects of loading frequencies on Aluminum 6061-T6 fatigue strength. Five groups of fatigue tests are conducted on the same specimen under the same cyclic axial load but at varying frequencies of 10 Hz, 20 Hz, 30 Hz, 40 Hz, and 50 Hz. Each group will have more than 30 tests. Then we evaluate the effects of load frequencies on material fatigue strength by comparing the distributions of the fatigue life. The T-Test is used to check whether the effects of load frequencies on the fatigue strength are statistically significant differences or not.